This invention relates to dry powder compositions suitable for use in electrographic recording. More particularly, it relates to heat-fusible and pressure-fixable one part developing powders that contain fluorinated carbon.
Known one-part developing powder formulations used in electrographic recording may be either heat-fusible or pressure-fixable. Heat-fusible developing powders are typically fixed after image formation by raising the temperature of the powder to its melting or softening point, causing the powder particles to coalesce, flow together, and adhere to the substrate. Pressure-fixable developing powders are typically fixed after image formation by simply applying pressure to the powder particles causing them to coalesce and adhere to the substrate.
Although both types of developing powders have been widely used and have enjoyed commercial success, they suffer from certain disadvantages that are related to their physical characteristics.
For example, the flow properties and developing characteristics of such powders are affected by the nature of the carbon black used therein. It has been found, for example, that when electrically resistive carbon black is employed, the developing powder has poor flow properties (i.e., it cakes and resists flow), especially in conditions of high humidity. Generally, the images produced with such powders have poor resolution, that is they exhibit fuzzy edge definition and image "fill-in" (i.e., toner deposits inside of letters such as A, B, D, O).
Additionally, such powders frequently form clumps in conditions of high humidity that may result in streaking on the finished copy. Still further, such powders are susceptible to clogging in the development station, leading to poor development and transfer of the developing powder and, consequently, poor copy quality.
Developing powders that employ conductive carbon-black also demonstrate poor flow properties and produce images that have poor resolution. Moreover, only low concentrations (e.g., about 0.5% by weight) of such carbon black can be utilized if an electrically resistive developing powder is desired. However, low carbon black concentrations are difficult to incorporate uniformly into the powder. Moreover, electrically conductive carbon black is hydrophilic in nature and this aggravates the poor flow properties of the developing powder compositions.
The foregoing disadvantages are overcome in the present invention. This is accomplished through the incorporation of fluorinated carbon into the developing powder composition.